Nov 06 2012

Seeing with Touch

The comic book hero Daredevil was blinded by a splash of radioactive waste, but the radioactivity (a common plot device of the time) also heightened his remaining senses. In addition to a form a echolocation, Daredevil was able to “see” by feeling his environment. How plausible is this idea?

While obviously not resulting in super powers, humans may have the ability to learn new senses. Researchers at the Weizmann Institute recently investigated whether or not people could learn to sense their environment with artificial “whiskers.” Rats and some other animals have a sensory organ humans do not, whiskers, with which they probe their environment. Researchers attached artificial whiskers with position and force sensors to the index fingers of subjects. They then sat the subjects between two vertical poles and asked them to detect with the whiskers which pole was farther back.

On the first day of testing the subjects were able to detect a difference in pole position of only 8cm. On the second day they learned to refine their probing techniques in order to detect a difference as small as 3cm.

I also have previously written about human echolocation – people who have learned to use a functional, if crude, form of echolocation to sense their surroundings.

What these two examples suggest is that vertebrate sensory processing is highly plastic. Our brains process multiple sensory streams in a complex way in order to build a model of the world. Further, the various senses are not just processed separately, but compared to each other in order to create one seamless experience of the world.

In addition, this latest research reflects the connection between our sensory input and our motor actions. This is not surprising – we experience this every day as so-called, “hand-eye coordination.” ¬†In the whisker experiment the subjects learned to modify their physical movements in order to ¬†optimize their probing – slowing down their finger movements, for example, in order to maximize the difference in timing between the two poles.

The question now is – what are the limits of plasticity in terms of learning new ways to process sensory information? Could a blind person, for example, learn to navigate their environment with their sense of touch alone. (OK, time for another geek reference – Miranda from Star Trek the original series was blind but navigated with a high-tech dress that allowed her to feel her environment.) To what extent will their brains be able to construct an actual image of the environment from such sensory information?

Research suggests that brain plasticity is fairly powerful, and while it continues throughout life it is greatest during childhood. Perhaps children who are born blind or become blind at a very young age could significantly develop their echolocation or tactile seeing ability.

All of this also demonstrates how animals can evolve new abilities. Creationists often make the argument from personal incredulity – how can new abilities evolve, because they would be of no use while in their incipient stages. But these examples show how untrue this is. Even a little bit of echolocation can have a survival advantage for a population moving to a niche with no or low light, and that provides an evolutionary toe hold to then improve and refine the new ability. In other words, plasticity can be a bridge to evolutionary changes.

Of course, humans also have technology. We can conceivably enhance new senses with technological aids in a synergistic fashion. In fact, neural plasticity allows us to imagine many ways in which we can merge humans and machines.

56 responses so far